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Old 01-03-2017, 02:07 PM   #1
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Default Supercharger And Effect On Emissions

Hi from the UK.
I took my car for a MOT today and it failed on Emissions.

It does this every year and then I use a cleaner like Cataclean and take it for a long run and it normally passes.

Just a thought and I hope someone can tell me the answer.
If I disconnect the Supercharger (as in remove the belt) what effect would it have on my emissions test?

When my pulley sheared many years ago I had to use my car and it just became like a standard MX-5 (Miata).
That's why I'm thinking what would happen to my emissions if I just took my supercharger belt off?

Could this be the answer to passing the MOT emission test?
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Old 01-03-2017, 03:02 PM   #2
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Full Disclosure - I'm replying from Canada.

I looked up the emissions testing for UK - this is what they do for vehicles newer than 1 August 1992
The first test consists of checking the emissions at ’fast-idle speed’ which involves running the engine at a speed of 2500 - 3000 rpm. During this test the emissions of CO and HC will be checked and a further check will be made on the lambda (1) value. The second test consists of a check of emissions at ‘normal idle speed’ in which the engine will idle between 450 and 1500rpm, but in this case only the CO emissions are assessed.

Before that date
For vehicles first used on or after 1 August 1975, emissions will also be checked using an approved analyser. After completing the visual test, the tester will use the analyser to assess the concentration of carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gases by inserting a sample probe into the exhaust tailpipe. The test is carried out with the engine at its normal idling speed and the analyser displays the results continuously. Once a stabilised figure is achieved the tester will record the result.

Are you running a factory ECU or some kind of aftermarket? Different injectors? Boost sensing piggy-back(s)? Other engine modifications? All of these will factor into your emissions.

The quick answer is: If you run a factory ECU with boost sensing piggyback(s) and no other modifications, then removing the belt and tying the by-pass valve open will give you (as near as makes no difference) a factory setup.
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Old 01-03-2017, 03:32 PM   #3
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I miss the old days when you could adjust the mixture by turning a screw.

Here's a link to my car info:

Supercharged MX5 Jasper Conran Special Edition "The Beast"

I have Greddy E-Management.

It failed on:
Fast Idle Test
CO result 0.60% (limit 0.3%)
Lambada result 1.037 (limits 0.970 - 1.030)

I have a new O2 sensor on the way.

They did the test twice the first results were:
CO result 0.65% (limit 0.3%)
Lambada result 1.051 (limits 0.970 - 1.030)

So readings did drop on the second test.

Just to add it was really cold here last night and I took the car in without taking it for a blast first.
I had trouble getting into my car as the doors had frozen solid.
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Old 01-03-2017, 04:21 PM   #4
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Ahh, the veritable BRP MP62. Looks just like mine used to....sniff.

That new O2 sensor should fix you right up.

If you still want to pull the belt (I doubt you'll need to) Do you have factory injectors? If so, e-manage is a piggy back. Disconnect and plug the vacuum hose, remove the belt, tie open the bypass valve.
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Old 01-03-2017, 04:37 PM   #5
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Fitting the sensor is not going to be easy with the charger in the way.

I think I have the original injectors.
I have no recollection of any paperwork saying otherwise.

When you say "disconnect and plug the vacuum hose" which hose are you referring to?
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Old 01-03-2017, 04:59 PM   #6
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The hose part shouldn't be necessary. Disconnecting the drive belt will keep the emanage from seeing boost and accomplish the same thing.
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Old 01-03-2017, 06:42 PM   #7
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Quote:
Originally Posted by sixshooter View Post
The hose part shouldn't be necessary. Disconnecting the drive belt will keep the emanage from seeing boost and accomplish the same thing.
Agreed, unless it is tuned to start below zero. It's a simple enough thing to disconnect the hose and be sure.

Little Badger, there will be a vacuum hose leading to the e-manage. Remove it from either the engine or the e-manage. Cap or plug the end going to the engine (so there is no vacuum leak).
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